Conventionally, a shunt resistor based current sensor has been proposed in which, in order to detect a pulse current, a large AC current, or the like, a current to be measured is flown through a shunt resistor portion the resistance of which is known, and a voltage drop produced in the shunt resistor portion is detected, whereby the magnitude of the current to be measured is detected. In a shunt resistor based current sensor of this kind, the resistance of the shunt resistor portion sometimes changes depending on the temperature. Therefore, the temperature of the shunt resistor portion is detected, and the resistance is corrected in accordance with the temperature. On a circuit board on which a voltage detection IC or the like for detecting a voltage drop is mounted, consequently, also a temperature sensor is mounted.
In Patent Literature 1, a busbar which is connected to the negative terminal of a battery functions also as a shunt resistor portion that is used for detecting a current of the battery. A temperature sensor is placed in the vicinity of two poles which detect the potential difference caused by the shunt resistor portion. The placement of the temperature sensor in the vicinity of the poles enhances the coupling characteristics with the temperature of the busbar.